Gina Miller photographed at her offices in London.
Photograph: Suki Dhanda for the Observer

Before we start the interview at her plush offices bang in the middle of South Kensington’s fashion district, Gina Miller has a question. “So,” she says, fixing me with a searching look, “was it the book you were expecting?”

The truth is, I had few expectations, because before I read her book, Rise: Life Lessons in Speaking Out, I hadn’t thought of Miller as a writer. To me, she was the woman who took the government to court over Brexit, succeeding in her bid to maintain the principle that parliament is sovereign. I admired her guts and resolve, but didn’t necessarily feel compelled to know her “story”. However, no one comes to public prominence these days without also being offered a book contract.

Unlike many famous people, Miller set out to write her book herself but, realising how difficult a task that was – what with being a businesswoman, campaigner, and mother – she recruited the journalist and novelist Elizabeth Day as a ghostwriter. Day, she says, is someone with whom she struck up an instant bond of trust, which she needed to speak honestly about her life.

If I look smart and I feel confident, other people’s bigoted assumptions have less power to harm me

Before I get to what I thought about the book, it’s perhaps more important to say what it made me think about some of my countrymen. There is a version of the modern British story that is all about reaching out, to use an annoyingly ubiquitous phrase. In this open and welcoming place, people are inclusive, tolerant, opposed to sexism, racism and all forms of bigotry, and discreetly proud of a tradition that honours justice and fair play. It’s a self-image many would like to see when a mirror is held up to the nation at large. Yet reflect for a moment on the examples Miller quotes from files of online comments about her, and that image quickly cracks.

“From the colour of your skin, you’re just a piece of shit,” reads one. “And shit should just be trodden on and I’m going to do that to your face.” Another informs her she is nothing “but a rich man’s whore”, who should be “locked up and taken out once a day for a good banging”. Then there is the warning that a “Jo Cox killing would be too good for you”, and the declaration that Miller is “not even human, just an ugly ape who needs whipping into obedience”.

“I was absolutely shocked,” Miller says about reading the files her lawyers had compiled for her. “I just didn’t know that those attitudes still existed, and I still find it shocking now.”

She writes in Rise that since going through the files, she has become “wary of walking down the street, of using public transport, of going out to public places”.

Well you would be, wouldn’t you?

In the book she refers to these messages as a “river of hate”. But that’s far too sanitising. They really constitute a cesspit of malice, containing all the very worst and most ignoble of human instincts. But what prompted this outpouring of moral sewage? Three things. First, Miller’s principled legal battle to uphold the rule of law following the Brexit referendum. Second, she was born in British Guiana (later Guyana). Finally, she is a woman.

Those three facts added together, two decades into the 21st century, made Miller a figure of toxic hatred. It probably didn’t help that she is an elegant-looking woman, and can sound a little haughty – or, at least, too carefully composed – when speaking on matters of constitutional importance. But they are minor issues, the kind that only take on significance once you’ve already decided you dislike someone.

‘I knew there would be a backlash, but I never thought that it would get that bad’: Gina Miller outside the supreme court after winning her Brexit case.
Photograph: Andy Rain/EPA

In person, Miller is not haughty. She’s neatly dressed, as you’d expect of someone in her line of work – she co-founded the investment firm SCM Direct and set up the True and Fair Campaign to monitor the City. The campaign’s aim is to “limit the possibility of future misselling or financial scandals through greater transparency”.

She places a firm emphasis on appearance in Rise. Her parents were fastidious people, and she describes her father, who became attorney general of Guyana, as “stately looking”, someone who “always prided himself on being beautifully turned out”. For her, clothes are more like armour. “If I look smart and feel confident,“ she writes, “other people’s bigoted assumptions have less power to harm me.”

This observation is delivered, like much else in the book, as a mixture of self-revelation and seasoned advice to other women. You could say Rise is a kind of old-fashioned feminist guide to corporate or professional advancement. In that respect, it’s no doubt pitched at the readership that bought Facebook chief operating officer Sheryl Sandberg’s Lean In in such vast numbers. It’s full of tips for women, gained through experience – often harsh experience – and backed up with statistics from various psychological studies of the kind that tend to reaffirm the blindingly obvious. Sample: “In 2014, Professor Karen Pine from the University of Hertfordshire also found that what you wear can boost or lower your self-esteem.”

But Miller’s story turns out to be an unusual and impressive one, and, if it were down to me, I would have preferred to have learned more about her life and received fewer life lessons. That said, I’m not her intended audience. When she writes “we”, she is usually referring explicitly to her fellow women.

The bare bones of her biography are that she grew up in Guyana in a strict (corporal punishment was used) but loving household, and she idolised her handsome and accomplished father. But aged 11, she was sent to England to board at an all-girls school in Eastbourne on the Sussex coast. She was bullied, but she “reached out” to her bully and they became friends. Her aim, she writes, was to “disarm” her tormentor with kindness. At 13, owing to currency restrictions in Guyana that meant a shortage of money at home, she worked as a chambermaid while still at school.

After school she studied law at the University of East London. Her ambition was to become a criminal barrister, but she quit the course following a vicious attack in the street – of which more later. She and her boyfriend, who was 10 years older than her, moved to Bristol and set up a photographic service for estate agents. They got married and had a child, Lucy-Ann. It was a difficult pregnancy and the baby suffered brain damage, which resulted in symptoms of autism, dyslexia and dyspraxia. The marriage ended in divorce five years later.

Now a single parent, she enrolled at the University of North London to study marketing, but also worked as a waitress and did several other jobs, including some modelling. In the final year of her degree, she met Jon Maguire, a City financier, and after she graduated they moved to Wiltshire and got married, which, she writes, “turned out to be one of the biggest disasters of my life”.

Even in that brief summary – and I haven’t come to the high drama and lowering fallout of the supreme court’s Brexit judgment – it’s apparent that Miller is more than familiar with life’s ups and downs. You can’t help but marvel at how she has ridden them out with what looks very much like poise and equanimity.

Yet there is also the suspicion that Miller skates over some of the more disturbing episodes of her life. The book is in large part a rallying call to women who have suffered setbacks, particularly at the hands of men, and yet the two major incidents of actual physical abuse she describes are dealt with so quickly that you could almost miss them, or certainly misunderstand what they entailed.

The first came with that attack when she was a student, which she describes in the book as “brutal”. She didn’t report it (not unusual for victims of violence) and recalls feeling “dirty, violated and in shock”. But what did the assault involve and why did it come about? Of this she says nothing in the book, except that some of the men who attacked her were students at her college. And even though the incident caused her to give up her degree course, and turn her back on her long-held dream, that’s all we learn of it.

Why the cursory retelling?

“I didn’t want people to feel sorry for me,” she says. I say that it’s perfectly possible, indeed common, to empathise with someone’s suffering and still admire them.

“But I have lots of detractors and they could use that,” she shoots back. “All the way through writing this book I had to have a sixth sense of how every word could be manipulated and used against me.”

I say that that sounds like a self-defeating way to go about writing a candid account of her life. She says she originally wrote a more graphic account, but decided she wanted the message to be about surviving rather than the assault itself. But, I learn, it is more complicated than that. She says there was a racist element to the attack. I try to establish what this means and, after a while, she says: “Well, I was attacked because I was not behaving like I was supposed to be behaving.”

But this doesn’t take us much further.

“I was being too western,” she says, when I ask her to explain.

So, I ask tentatively, the racism was not from a white group of students?

She shakes her head. They were Asian, she says, and they had mistaken her for being Indian. “That brings up a whole different element, and I thought, especially in the time we’re living in at the moment, I just don’t feel that’s the right thing to talk about right now.”

The sensitivity seems misplaced, not least because the book puts a high premium on speaking your mind and telling the truth, regardless of how people might respond. Indeed, she goes so far as to suggest that the way to go forward towards hope in life is by “shaming the abusers and the bullies; by calling out and shaming people who do bad things”.

I say I’m not so sure about the value of “shaming”, but perhaps she could have shown solidarity with people living in communities where they are obliged to follow codes of behaviour that they do not wish to follow. Perhaps they too want to rise above the social constraints placed on them.

“That’s something that I’m learning about,” she says, ”but I was totally unaware when I was student and I didn’t know what was going on. I’m realising now that it’s much more prevalent than I thought it was.”

The other alleged incident involves her second husband, Jon Maguire. It is written in an oblique, impressionistic style.

“I remember the coldness of the floor. I remember the hardness of the slate pressing against my side,” is the key image of the relevant passage. It comes from the chapter in which, she says, she had most help from Day.

Elsewhere, she mentions “emotional abuse”, but she obviously intends the reader to derive more than that from the scene. When I put this to her, she says that “the message in that chapter is that domestic violence does not happen to just stupid women”.

Maguire disputes Miller’s claims of abuse, and counters with an allegation that she had a drink problem during their marriage, which she in turn denies.

Whatever happened, she fled him, taking Lucy-Ann. They slept in B&Bs and sometimes in her car in a multi-storey car park. Eventually she approached Lucy-Ann’s father, who found a flat for them in the same block in which he lived in Tooting. Thereafter she had no more to do with Maguire, but in 2010 he stood as a candidate for the English Democrats at the general election. Their manifesto called for an end to “so-called asylum seekers”, and a separate parliament for England.

He doesn’t sound like a perfect match for Miller, yet she fell head over heels with the man. As she writes: “For the first and last time in a relationship, I was completely honest with my partner, revealing all my weaknesses.”

I ask her what her third husband and business partner, Alan Miller, thinks of that. She says she told him from the outset that she would never be able to reveal herself so fully again. “I said to him: ‘You’re not going to get the full, soft Gina.’”

She says this is a common self-protective reaction among survivors of domestic violence. If she had met Miller first, she believes things would have been different.

“But I can’t wind back the clock and change that. I can only say this is what happened.”

Her marriage to Miller, with whom she has two children, is a happy one. She was keen to acknowledge his decency in the book because she wanted to say that “there are good men out there as well”.

It’s for this reason that she is not fully signed up to #MeToo – a movement that she says has “conflated too many things”. Yet she writes a whole chapter, entitled #MeToo, detailing sleazy behaviour she has suffered at the wandering hands of predatory men.

“I just want people to be equal and fair to each other,” she says.

Of course, the problem is what to do when people are not equal, or not fair to each other. Rise doesn’t really get to grips with that question – or rather, it gives contradictory advice. Be nice to bullies, she argues at one point, because they are likely to be hurting themselves and an act of kindness can break the cycle. She also, as mentioned, talks about shaming them. Yet, in the two cases she cites where she was on the wrong end of men trying to sexually exploit their corporate power, she did neither. On the first occasion, she was shocked into horrified retreat from a Harvey Weinstein-type hotel-room-and-bathrobe scenario. In the second, she kept quiet to protect an “obnoxious fund manager’s” family from the fallout of a public allegation. She says both men have since changed their behaviour – partly, she suggests, because they know that she knows. If so, that hasn’t been the pattern of behaviour among sexual predators who have come to light in recent times. In those cases, close shaves have only emboldened them.

What of the current paralysis over Brexit? She is alarmed that the government is running out of time to secure a deal. And no deal, she says, is something she doesn’t see “how we would survive”. But because she also doesn’t see a way to reach a deal that will satisfy enough people, she thinks there is a good chance of a second referendum. “I think it’s the only way out. Politicians want to get out of this mess unscathed and preserve themselves, because that means they fight another day. The way you do that is you take the decision and you give it back to people and say: ‘Well, it’s not our decision. It’s their decision.’”

Perhaps, but how will that change the situation, especially if, as seems likely, it would be a close call once more? “I think there needs to be an amnesty,” she says.

I silently contemplate what that might mean – perhaps people can declare their offensive tweets to the authorities without fear of sanction – before asking her.

“Whatever the outcome,” she explains, “everybody is going to have to agree, that’s it. We stop campaigning until the next election or whenever the time is, and we actually have to find a way through it together, because you can’t carry on like this. I mean everyone is feeling either exhausted, stressed, resigned. These emotions are very destructive.”

Regardless of the outcome, she says, there should be no further referendums after the second one. It’s an idea, certainly no more fanciful than many of the measures the government has put forward. But whatever its merits, I can’t imagine the current leader or government could make the case for it and continue in office. So if it were to happen, it probably would not be as a result of political self-preservation.

Still, it would be wise to take note because, according to Miller, she saw where the last referendum was heading before the Remain campaign realised what was going on. She worked for the Remain team but, she says, was sidelined in the run-up to the referendum because she believed its facts-and-figures approach wasn’t working outside London.

“I was replaced by more ‘obedient’ women,” she writes. Is that true? “Yes,” she says. “Because I wasn’t speaking to the script, I stopped being asked to speak.”

Miller has also left the Labour party, for whom, she says, she and her husband worked on the 2015 manifesto, drafting the section on pension reform. She quit Labour more than a year ago, “when the antisemitic stuff started coming to the surface”. She insists that she has no ambition to become a politician in any existing or new party, and nor, if it were offered, would she join the House of Lords.

“I’m more interested in policy than politics, and I can do that as an independent person,” she says. She is at pains to point out that she never sought the public spotlight. The reason she became a figurehead for the legal challenge to the government was because she was approached by the law firm Mishcon de Reya, who asked if she would be a claimant in the case. There were two other claimants at that stage, men she describes as “very powerful, successful and publicly known”. But they dropped out, fearful of the repercussions.

“It’s completely the right thing for them to have done,” she says. “It would have destroyed them. I mean, it’s all very well me getting what I was getting, but for them to do it, it would have been disastrous.”

Why would it have been worse for them than you?

“Because at that time I wasn’t as publicly known. I knew there would be a backlash, but I never thought that it would get that bad.”

That, in a nutshell, is the overriding message of Rise: stand up for your beliefs, don’t be cowed by bullies, face down your fears. It’s repeated throughout, and the role model for this behaviour, of course, is Miller herself. That could easily come across as boasting, but she offsets the self-promotion with the various setbacks, self-doubt and failures with which she’s also had to deal.

The idea of the book is that all women are a bit like Gina, or could be. But despite the rousing, Hollywood-style rallying call – “dare to dream, dare to aim high, we must dare to also face our weakness” – the reader is inevitably left with the impression that Miller is a good deal more resilient, principled and determined than most people.

And in many ways, she is. It cannot have been easy to come to a foreign land as an 11-year-old without your parents, or to get on with life after being attacked and dropping out of her law degree, or to be a single parent of a child with disabilities, or to survive the abuse that she has. But to withstand being public enemy No 1 to the Brexit half of the country, and the terrifying threats and appalling insults aimed at her, takes real courage; to do so while maintaining a calm and collected exterior requires a very large bank of sang-froid.

For all her coolness, I warmed to Miller, if not her book. It sings a familiar song of triumph over adversity, but has too many missing notes to be wholly convincing. She is someone who keeps herself together by holding back her innermost self. That’s probably quite wise in a public figure, not entirely ideal in a romantic partner, but seldom a quality that’s welcome in an author.

“I believe in you. I believe in us. I believe we all can rise,” are the final sentences of the book, sounding like a Whitney Houston lyric.

It would be nice if that were true. But I believe that the trajectory of the extraordinary Gina Miller is set to continue upwards.

•Rise: Life Lessons in Speaking Out is published by Canongate (£16.99). To order a copy for £11.99 go to guardianbookshop.com or call 0330 333 6846. Free UK p&p over £10, online orders only. Phone orders min p&p of £1.99